Thread cutting device for sewing machines



June 9, 1964 KlYoYuKl MIYAKE 3,136,276

THREAD CUTTING DEVICE FOR SEWING MACHINES Filed Dec. 6, 1962 2 Sheets-Sheet l KEI( 3 \46/(45\ \43 60 ss'f 52 4847 49 44 V l 69 `72 ll June 9, 1954 KlYoYuKl MIYAKE 3,136,276

THREAD cu'mNG DEVICE FOR SEWING MACHINES Filed Dec. 6, 1962 2 Sheets-Sheet 2 MMM( United States Patent O ce Eim l A Patented June 9, 1964 FIG. 2 is a side view of a moveable thread cutting THREAD cUT'ruSZ/icn non sil-:WING means;

MACHENES FIG. 3 1s a slde view showing a pulling arm of thls de- Kiyoyuki Miyake, 541 Heiwa-machi, Kurashiki-shi,

. Okayama-keu, Japan Fiied Dec. 6, 1962, Ser. No. 242,340 1 Claim. (Cl. 112-252) The present invention relates to sewing machines and more particularlyy to a device for cutting sewing threads after sewing or stitching operations.

It has been customary in the prior art to use a separate cutting means, such as, scissors, knives or the like to cut sewing threads upon termination of the stitching operation. In order to avoid such troublesome and time-consuming operations, there have been proposed some sewing machines wherein the cutting operation of the threads was eifected Without the aid of any independent cutting means. However, none, when carried into practice, have been proved satisfactory when the following points are taken into consideration. That is, the cutting olf of the threads is required to be effected at such a spaced point from the needle that the threads will not slip out of the thread eye of the needle. The distance between such cutting point and the needle, therefore, should preferably be always constant. If such distance is too long, the ends of the threads will remain danglingly on the stitched material. This defect has been experienced in the past since the pulling or stretching operation of the threads was poorly done.

When it was necessary to cut threads before the stitching had been carried out to the material edge, the operation was time consuming in that the threads had to be cut oif at both sides of the material from time to time.

Moreover, in the case of automatic sewing machines of the prior art, it was difficult to stop the operation of the machine whenever it was necessary to cut the thread.

The present invention aims to eliminate the foregoing defects and has for its object a means of cutting the threads upon termination of the stitching operation, said means comprising a simple stepping operation of a treadle and maintaining the threads in a suitably stretched position in order to keep an adequate length of the threads between the point where the threads are to be cut and the needle, so that the needle thread will not be disconnected from the thread eye of the needle as the same is raised in the next succeeding stitching operation.

A further object of this invention is to effect the cutting operation of the threads at the bottom side of the material, thus improving the external appearance of the stitched material without permitting any odd ends of the thread to appear on the surface of the material.

A still further object of this invention is to provide an improved means for quickly and readily breaking the stitching operation immediately before the cutting operation of the threads.

Other objects and advantages of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification, wherein like reference characters designate corresponding parts in the several views and in which:

FIG. 1 is a longitudinal View of a sewing machine according to this invention;

vice;

FIG. 4 is a plan view of a throat plate on an enlarged scale;

FIGURE 5 is a longitudinal view showing a clutch mechanism in connection with a motor partly in crosssection; and,

FIGURE 6 is a longitudinal cross-sectional view illustrating the cutting mechanism and a part of the bed plate.

FIG. l of the drawing shows the main body 11 of a sewing machine of the conventional type, and comprises the head, arm and upright portions. A needle 12 is supported in a usual manner by said main body 11 and is mechanically connected with reciprocating means, not shown, designed to move the needle up and down. The main body is on a bedplate 15 and has a throat plate 14 having an aperture 13 through which the needle 12 can pass.

As shown in FIG. 4, the throat plate 14 is also provided 4with two narrow openings 16 and 17 which are positioned in a parallel relation with respect to each other so as to hold the aperture 13 therebetween, and into which feeddog means of a conventional mechanism are respectively set, said feed-dog means being designated by 18 and 19. At a portion on the same axis of the aperture 13 of the throat plate with respect to the direction of the movement of the material to be so sewn, there is a cutting aperure 21. Said cutting aperture is made slightly wider than the aperture 13, and a connected with the same by means of an opening 20 adapted to guide the threads. Both moveable and stationary thread cutting means are provided. Underneath the throat plate 14 is provided a cutting plate 22 having a thread cutting blade 23. Said thread cutting plate 22 is suitably fastened to the under surface of the throat plate 14 with a rivet or the like, and positioned such that the thread cutting blade 23 of the stationary thread cutting means is visible in cutting aperture 21 at a side close to the aperture 13, as viewed in FIG. 4. At the opposite side of the cutting aperture 21 with respect to the aperture 13, there is a rectangular aperture 24, in such a manner that the longer side of said rectangular aperture will make a right angle with respect to the direction of the feed-dog means y18 and 19. A moveable thread cutting blade 25 is located underneath the rectangular aperture 24 and adapted to be lifted vertically through said aperture 24 by treadle means so as to cut the threads.

The rectangular aperture 24 and the aperture 13 are so separated as to maintain'a suificient length of the threads between the cut point and the thread eye, in order to prevent the cut end of the thread from slipping out of its connection with the thread eye.

As shown in FIG. 2, the moveable thread cutting arm 25 which is adapted to vertically slide through the rectangular aperture 24 comprises the vertical section 26 and the sideward extending portion 27 so as to form an arc-shaped blade 29, said portion 27 extending sideward at the upper portion of said vertical section Z6.

FIG. 3 shows a thread stretching arm 30 consisting of the vertical section 31 and the sideward extending portion 32 which are made substantially identical in shape to the moveable thread cutting arm 25 except that the portion corresponding to the arc-shaped blade 29 of the moveable thread cutting arm has no cutting edge and is made slightly larger than said arc-shaped blade. The moveable thread cutting arm 25 and the thread stretching arm are assembled in such a manner that one side of the cutting arm where the arc-shaped blade 29 is located will face the thread stretching arm. These two arms 25 and 36 are tightly secured on an L-shaped arm 36 shown in FIG. 1, by means of holes 28 and 33, and suitable fastening means (not shown). As shown in FIG. 6, the one side of the cutting arm ZS is designed to vertically slide as at 34 on one side of the rectangular aperture 24 while one side of the stretching arm 30 is adapted to pass along one side of aperture 24 with suiiicient space to permit the thread to pass through in between. The si-deward extending portion of L-shaped arm 36 is tightly secured on a rod 39 vertically extending parallel with said arm 36. The uppermost portion of said rod 39 is partly inserted into a hole 76 in such a manner that when said rod is lifted it will be further inserted into the hole 76, the hole being provided in a suitable supporting member 77 securely disposed on the under surface of the bedplate 15.

4I designates a stopper the upper portion of which is secured on the under surface of the bedplate, and the lower portion of which is provided with a horizontally extending section having a hole 42 penetrating therethrough and adapted to receive the lower portion of the rod 3% which projects downwardly from the connecting arm 36. The upper portion of the rod 39, which extends upwardly from the sideward extending portion of the L.shaped connecting arm 36, is provided on its outer circumference with a spring 38 along its entire portion. each end of said spring being supported by the supporting member '77 and the sideward extending portion 36 of the connecting arm, respectively. Owing to the action of said spring 38, the cutting arm 25 and the stretching arm 3@ are held in their unlifted position as shown in FIG. l. The bottom of the rod 39 is in face contact as at 44 with an arm 43 which is supported bya bracket 45, said arm 43 being adjustable by means of an adjusting screw designated by 4S. Said bracket 45 is axially supported on the projection 47 of a horizontal lever 46 and secured thereon by means of a screw 49, projection 47 extending from one end of said horizontal lever 46. The horizontal lever 46 is pivotally connected with frame 10 by means of a screw 50 approximately at the center of its entire length, and mechanically related to a treadle 54 through vertically slidable rods 53 and S3 which are adjustably clamped by suitable clamp means.

Referring now to the clutch mechanism, a motor 60 is provided under the bedplate by suitable fastening means (not shown), as shown in FIGS. l and 5. The shaft 61 of the motor 60 is connected with a main shaft 63 by friction gearing 62, said main shaft 63 being housed in and supported by the housing 64 of the motor, in such a manner that it will move horizontally. The main shaft 63 is provided on its outmost portion with a pulley 78 which is connected to the main body of the machine by a belt .65 trained a pulleyV on the main drive shaft. The main shaft 63 is partly reduced at a portion close to the pulley 73 so as to form a groove 66. A fork arm 67 is next to groove 66 and on the inner face of said fork arm 67 is pivotally mounted a sliding wheel 68 which is adapted to slidably contact with the main shaft and move the same outwardly when the main shaft 63 is required to be moved horizontally. The fork arm 67 is secured at one end to the upper portion of the vertical section 7i) of a connecting arm 69, said vertical section being axially connected to the housing 63 of the motor. Theother end of the connecting arm is connected to a clutch treadle 73 through vertically slidable rods 72 and 72 which are adjustably clamped together by means of suitable clamp means. The clutch treadle '73 is always inclined at its further end owing to the action of spring 74 placed thereunder at the side closest to the operator.

In operation of the driving means, the starting of the motor 6@ is done by a suitable switching means not shown.

In the above case, owing to the action of the spring 74 which is adapted to push the clutch treadle 73 upwardly and make the treadle inclined at its further side, the'vertically slidable rods i2 and 72 are held in their original position. Accordingly, owing to the provision of the projection which projects horizontally from the housing of the motor, and axially supports the vertical section 70 of the connecting arm 69, the upper portion of said vertical section 76 is pushed to the direction of the motor, thus engaging the friction gearing 62 with the rotation of the motor through the main shaft 63. Therefore, when the motor is turned on, its rotation is directly given to the pulley 78 which is mechanically connected with the stitching mechanism through the belt 65. When the stitching operation is to be temporarily stopped for the purpose of cutting the threads, the clutch treadle 73 is pressed. Then the rods 72 and '72 are lifted. And through the connecting arm 69 and the main shaft 63, the engagement between the motor and the friction gearing is disconnected. rl`hen the cutting operation of the threads Vmay be carried out in thev manner described. Thus a break of the stitching operation can be readily eected by stepping down on treadle 73. When the treadle 73 is released, it will be restored to its original position by the action of the spring 74.

When the 'threads are to be cut in the middle of the material, the cutting plate 22 of an nnmoveable type may be used instead of the device above-mentioned. By drawing the material towards the operator, by hand, in order to guide the threads toward the cutting aperture 21 along the narrow opening Ztl, and then drawing the material back again to the direction of the needle, the threads will readily be cut by the blade 23. In this case, the needle is withdrawn from the material.

Although the present invention has been described in conjunction with its preferred embodiment it is to be understood the modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand, such modifications and variations are considered to be within the purview and scope of the invention and appended claim.

What I claim as new and desire to secure by Letters Patent of the United States is:

In a sewing machine having an eye-type needle and a bedplate with at least one recess therein, said sewing machine being driven by a motor having a shaft turning a pulley which in turn drives theV sewing machine by bel'ting, a thread cutting attachment for cutting thread at the underside of material and at some distance from the sewing machine needle eye, comprising in combination,

a throat plate on the sewing machine for passing thereon material to be sewn including a needle aperture for the needle to pass through, a pair of longitudinal apertures on both sides of the plate for receiving feed-dog means to move the material forward and a rectangular aperture at some distance from the needle aperture along the path of travel of said material; an L-shaped cutting arm and an L-shaped stretching arm, the interiors of said arms being shaped like sickles, the cutting arm having an arcuate internal blade, the portion of the stretching arm corresponding to said blade being dull and slightly larger than the blade, said arms being mounted in side-by-side relation, approximately coinciding, and disposed so as to pass at right angles through said rectangular aperture; an L-shaped connecting arm, said cutting and stretching arms being fastened to the top thereof, there being an aperture in the bottom thereof for aixng a rod therein, a rod passing through said aperture and being received in said bedplate recess, and spring means around said rod urging said connecting arm to a position where said cutting and stretching arms are not through the rectangular aperture in 'the throat plate;

a treadle and connecting means connected to said rod to push said rod upwards so that said cutting and stretching arms pass upwards through said aperture to grab the thread; and,

pedal clutch means adapted to release said pulley from said motor drive so that said thread can be cut without stopping said motor.

References Cited in the tile of this patent UNITED STATES PATENTS Dennis et al. Feb. 6, 1866 Hogan Apr. 19, 1904 Coley Dec. 17, 1912 Sullivan et a1. Aug. 31, 1915 Kendall Oct. 14, 1924 Galkin July 22, 1947 Hale Mar. 27, 1951 FOREIGN PATENTS Great Britain Mar. 15, 1961 

